Patients with respiratory ailments are often treated with respiratory assist devices that deliver supplemental breathing gas to the patient. Such devices may deliver gas to the patient using high flow therapy (HFT). HFT devices deliver breathing gas at a high flow rate via an interface such as a nasal cannula to increase the patient's fraction of inspired oxygen (FiO2), decrease the patient's work of breathing, or do both. That helps the patient recover from respiratory ailments, such as respiratory distress or bronchospasms. Some HFT devices heat and humidify the delivered breathing gas for medical reasons (e.g., to maintain the pliability of the tissues of surfactant-deficient patients, or to preserve mucosal integrity) or to reduce patient discomfort.
A challenge associated with delivering breathing gas via a high-flow system is managing heated and humidified gas that is carried to the patient. During transport of heated and humidified breathing gas, moisture from the heated and humidified breathing gas can condense and form liquid droplets. Condensation in a ventilation circuit presents both clinical and mechanical challenges. The condensate can accumulate in the gas circuit and thus limit flow through the system. Movement of accumulated condensate liquid in the gas circuit into the patient can present a risk of aspiration. Additionally, the condensate can collect and stagnate, posing a biohazard.
One solution is to heat the tube carrying the humidified breathing gas from a supply unit to a patient interface. The heating can be done using a heated water jacket or using a heated wire disposed within the tube. Tubes with heated water jackets can be heavy due to the weight of the water in the tubes. Additionally, tubes with heated water jackets require a pump capable of circulating the heated water through the tube, which increases the overall complexity and cost of the respiratory therapy system. Additionally, tubes having heated wires require a connection to an electrical power source which adds to the complexity and cost of the respiratory therapy system. Heated wires present in a tube may also pose a safety hazard if the wires overheat.